Yoshiaki Kurokawa

Cleaning by Brush-Scrubbing of Chemical Mechanical Polished Silicon Surfaces Using Ozonized Water and Diluted HF

A new process for scrubbing chemical-mechanical-polished silicon wafer surfaces with a brush (brush-scrubbing process) was developed. The scrubbing is performed in two stages; the first stage involves a wet treatment using ozonized water and dilute HF. The second stage involves scrubbing with a Poly(vinyl alcohol)(PVA) brush. After scrubbing, the number of residual particles, metal and carbonaceous contamination, and surface roughness of the silicon wafer surface were evaluated. It was determined that this new brush-scrubbing process efficiently removed particles from chemical mechanical polished silicon surfaces. Finally, a model explaining the new brush-scrubbing process is constructed.

Two-Dimensional Modulation Code for Multilayered Waveguide Holographic Memory

Our two-dimensional modulation code improves the decoding accuracy of images reconstructed from a multilayered waveguide holographic memory that have been translated, rotated, and distorted with respect to the image detector. The reconstructed images can be decoded without using a precision mechanical structure or an imaging mechanism that matches pixels of the reconstructed images to the pixel grid of the image detector. This code also improves the bit error rate of distorted reconstructed images and reduces crosstalk among different layers and image detector saturation.

Effects of head parameters on read/write characteristics of perpendicular/longitudinal composite media

The effects of the saturation flux density (Bs) of a read/write head on the recording characteristics of a perpendicular/longitudinal composite medium were investigated. It was found that the recording sensitivity was improved by applying the higher Bs head. In the higher density region, the reproduced-voltage-enhancement was enlarged with the high Bs head, however, in the higher MMF region, the read/write characteristics were worse because the head field penetration becomes broad. Therefore, it is necessary to take into account the head parameters when optimizing the medium parameters.

Effect of perpendicular layer thickness on read/write characteristics of perpendicular/longitudinal composite media using ring-type head

The effects of perpendicular layer thickness on remanent magnetization states and recording characteristics of perpendicular-longitudinal composite media were investigated. The contribution of perpendicular magnetic reversal is varied due to a change in the thickness of perpendicular layer; the transition length of the thinner perpendicular layer medium was broader than that of thicker perpendicular medium. The medium with thicker perpendicular layer shown better performance not only in recording density response but also peak shift characteristics. In order to realize excellent read/write characteristics, optimization of the thickness of perpendicular layer becomes one of the important factors, in addition to the optimization of the underlayer parameters.

Optimization of head-medium parameters for electroless CoNiReP/NiFeP double-layered media using ring-type heads

Abstract Optimization of head/medium parameters for perpendicular recording on the electrolessly deposited CoNiRep/ NiFeP double-layered (DL) media was examined in combination with ring-type heads. Higher reproduced voltage was obtained in the DL medium with higher underlayer coercivity, H c (u), (160 Oe) due to the ‘phase sychronization’ (PS) effect. It was necessary to adjust the perpendicular magnetization layer thickness, δ p , in accordance with the head B s in order to obtain sufficient PS effect. In the higher recording density region, the combination of a small gap head (0.08 μm) and a medium with thicker δ p (0.3 δm) and lower H c (u) (50 Oe) was optimal, due to higher crystal orientation at the medium surface and improvement of head field penetration.

Pit Distribution Design for Computer-Generated Waveguide Holography

Multilayered waveguide holography (MWH) is one of a number of page-oriented data multiplexing holographies that will be applied to optical data storage and three-dimensional (3D) moving images. While conventional volumetric holography using photopolymer or photorefractive materials requires page-by-page light exposure for recording, MWH media can be made by employing stamping and laminating technologies that are suitable for mass production. This makes devising an economical mastering technique for replicating holograms a key issue. In this paper, we discuss an approach to pit distribution design that enables us to replace expensive electron beam mastering with economical laser beam mastering. We propose an algorithm that avoids the overlapping of even comparatively large adjacent pits when we employ laser beam mastering. We also compensate for the angular dependence of the diffraction power, which strongly depends on pit shape, by introducing an enhancement profile so that a diffracted image has uniform intensity.

Evaluation of Double-Layered Magnetic Recording Medium Composed of Perpendicular and Longitudinal Anisotropy Layers

A double-layered (DL) medium composed of a CoNiReP perpendicular anisotropy top layer (0.20 µ m thick) and CoP longitudinal anisotropy underlayer (0.05 µ m thick) was fabricated and its recording characteristics were investigated with a combination of a ring-type head. The reproduced voltage of the DL medium was enhanced to be larger than that of the simple summation of the reproduced voltage of the CoNiReP single-layered medium and that of the CoP one. Moreover, the reproduced waveform of the DL medium showed a single peak pulse and it did not change even at higher recording magnetomotive force (MMF). These results suggest that the reproduced voltage enhancement comes from the phase synchronization effect even at higher recording MMF.

Two-fluid cleaning technology for advanced photomask

Along with the increased miniaturization of electronic devices, two-fluid cleaning technology is garnering the spotlight as a solution for the manufacturing process of Photomask. This is because it is now known that implementing energy control of the particles that are sprayed on the substrate allows cleaning of miniature patterns. However, it is not yet clear just how miniature of a pattern is cleanable with two-fluid cleaning technology. This study discusses mechanisms to miniaturize the droplets created by a two-fluid nozzle. In addition, this study also considers the impact of droplet size on pattern damage to the Photomask and speaks on the potential for applying two-fluid cleaning technology in the future.

Study on EUV photomask resist stripping and cleaning

Any cleaning technology for state-of-the-art photo masks requires that pattern damage does not occur and optical characteristics do not change. Particularly with EUV masks, an important challenge is to suppress/prevent changes to the optical characteristics of ruthenium (Ru) film that generates when resist is removed (separated). This report illustrates a model explaining why optical characteristics change when conventional resist removal (separation) technologies are used on EUV mask. It also proposes a new resist removal technology that allows resist to be removed without any optical damage to Ru films.

Two-Dimensional Constant-Weight Block Code in Orthogonal Aperture-Multiplexing for Multilayered Waveguide Holographic Memory

For a two-dimensional constant-weight block code, we show that the recording density is proportional to code rate and the second power of the size of the bright point. Second, we show four constant-weight block codes (two 2:16 codes, a 4:24 code, and a 4:16 code) with different code rates. In simulation experiments, we measured the maximum size of bright points for each code, the bit error rate was practical (10-4 or less), and simulation results show that the maximum size increases as the code rate decreases. Then, we show that the highest recording density is achieved with the two 2:16 codes and the 4:24 code and that these codes are suitable for orthogonal aperture-multiplexing. We also show that there is a trade-off between multiplexity and the code rate.